Methods to Improve Leakage of High K Materials

ABSTRACT

A method for reducing the leakage current in DRAM Metal-Insulator-Metal capacitors includes forming a capacitor stack including an oxygen donor dopant incorporated within the dielectric layer. The oxygen donor dopants may be incorporated within the dielectric layer during the formation of the dielectric layer. The oxygen donor materials provide oxygen to the dielectric layer and reduce the concentration of oxygen vacancies, thus reducing the leakage current.

This document relates to the subject matter of a joint researchagreement between Intermolecular, Inc. and Elpida Memory, Inc.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to the field of dynamic randomaccess memory (DRAM), and more particularly to methods of forming acapacitor stack for improved DRAM performance.

BACKGROUND OF THE DISCLOSURE

Dynamic Random Access Memory utilizes capacitors to store bits ofinformation within an integrated circuit. A capacitor is formed byplacing a dielectric material between two electrodes formed fromconductive materials. A capacitor's ability to hold electrical charge(i.e., capacitance) is a function of the surface area of the capacitorplates A, the distance between the capacitor plates d, and the relativedielectric constant or k-value of the dielectric material. Thecapacitance is given by:

$\begin{matrix}{C = {{\kappa ɛ}_{o}\frac{A}{d}}} & \left( {{Eqn}.\mspace{14mu} 1} \right)\end{matrix}$

where ∈_(o) represents the vacuum permittivity.

The dielectric constant is a measure of a material's polarizability.Therefore, the higher the dielectric constant of a material, the moreelectrical charge the capacitor can hold. Therefore, for a given desiredcapacitance, if the k-value of the dielectric is increased, the area ofthe capacitor can be decreased to maintain the same cell capacitance.Reducing the size of capacitors within the device is important for theminiaturization of integrated circuits. This allows the packing ofmillions (mega-bit (Mb)) or billions (giga-bit (Gb)) of memory cellsinto a single semiconductor device. The goal is to maintain a large cellcapacitance (generally ˜10 to 25 fF) and a low leakage current(generally <10⁻⁷ A cm⁻²). The physical thickness of the dielectriclayers in DRAM capacitors could not be reduced unlimitedly in order toavoid leakage current caused by tunneling mechanisms which exponentiallyincrease as the thickness of the dielectric layer decreases.

Traditionally, SiO₂ has been used as the dielectric material andsemiconducting materials (semiconductor-insulator-semiconductor [SIS]cell designs) have been used as the electrodes. The cell capacitance wasmaintained by increasing the area of the capacitor using very complexcapacitor morphologies while also decreasing the thickness of the SiO₂dielectric layer. Increases of the leakage current above the desiredspecifications have demanded the development of new capacitorgeometries, new electrode materials, and new dielectric materials. Celldesigns have migrated to metal-insulator-semiconductor (MIS) and now tometal-insulator-metal (MIM) cell designs for higher performance.

Typically, DRAM devices at technology nodes of 80 nm and below use MIMcapacitors wherein the electrode materials are metals. These electrodematerials generally have higher conductivities than the semiconductorelectrode materials, higher work functions, exhibit improved stabilityover the semiconductor electrode materials, and exhibit reduceddepletion effects. The electrode materials must have high conductivityto ensure fast device speeds. Representative examples of electrodematerials for MIM capacitors are metals, conductive metal oxides,conductive metal silicides, conductive metal nitrides (i.e. TiN), orcombinations thereof. MIM capacitors in these DRAM applications utilizeinsulating materials having a dielectric constant, or k-value,significantly higher than that of SiO₂ (k=3.9). For DRAM capacitors, thegoal is to utilize dielectric materials with k values greater than about20. Such materials are generally classified as high-k materials.Representative examples of high-k materials for MIM capacitors arenon-conducting metal oxides, non-conducting metal nitrides,non-conducting metal silicates or combinations thereof. Thesedielectrics may also include additional dopant materials.

A figure of merit in DRAM technology is the electrical performance ofthe dielectric material as compared to SiO₂ known as the EquivalentOxide Thickness (EOT). A high-k material's EOT is calculated using anormalized measure of silicon dioxide (SiO₂ k=3.9) as a reference, givenby:

$\begin{matrix}{{EOT} = {\frac{3.9}{\kappa} \cdot d}} & \left( {{Eqn}.\mspace{14mu} 2} \right)\end{matrix}$

where d represents the physical thickness of the capacitor dielectric.

As DRAM technologies scale below the 40 nm technology node,manufacturers must reduce the EOT of the high-k dielectric films in MIMcapacitors in order to increase charge storage capacity. The goal is toutilize dielectric materials that exhibit an EOT of less than about 0.8nm while maintaining a physical thickness of about 5-20 nm.

One class of high-k dielectric materials possessing the characteristicsrequired for implementation in advanced DRAM capacitors are high-k metaloxide materials. Titanium dioxide and zirconium dioxide are two metaloxide dielectric materials which display significant promise in terms ofserving as high-k dielectric materials for implementation in DRAMcapacitors. Other metal oxide high-k dielectric materials that haveattracted attention include aluminum oxide, barium-strontium-titanate(BST), hafnium oxide, hafnium silicate, niobium oxide,lead-zirconium-titanate (PZT), a bilayer of silicon oxide and siliconnitride, silicon oxy-nitride, strontium-titanate (STO), tantalum oxide,or combinations thereof.

Generally, as the dielectric constant of a material increases, the bandgap of the material decreases. This leads to high leakage current in thedevice. As a result, without the utilization of countervailing measures,capacitor stacks implementing high-k dielectric materials may experiencelarge leakage currents. High work function electrodes (e.g., electrodeshaving a work function of greater than 5.0 eV) may be utilized in orderto counter the effects of implementing a reduced band gap high-kdielectric layer within the DRAM capacitor. Metals, such as platinum,ruthenium, and ruthenium oxide are examples of high work functionelectrode materials suitable for inhibiting device leakage in a DRAMcapacitor having a high-k dielectric layer. The noble metal systems,however, are prohibitively expensive when employed in a mass productioncontext. Moreover, electrodes fabricated from noble metals often sufferfrom poor manufacturing qualities, such as surface roughness, pooradhesion, and form a contamination risk in the fab.

Leakage current in capacitor dielectric materials can be due to Schottkyemission, Frenkel-Poole defects (e.g. oxygen vacancies (V_(ox)) or grainboundaries), or Fowler-Nordheim tunneling. Schottky emission, alsocalled thermionic emission, is a common mechanism and is theheat-induced flow of charge over an energy barrier whereby the effectivebarrier height of a MIM capacitor controls leakage current. Theeffective barrier height is a function of the difference between thework function of the electrode and the electron affinity of thedielectric. The electron affinity of a dielectric is closely related tothe conduction band offset of the dielectric. The Schottky emissionbehavior of a dielectric layer is generally determined by the propertiesof the dielectric/electrode interface. Frenkel-Poole emission allows theconduction of charges through a dielectric layer through the interactionwith defect sites such as vacancies, grain boundaries, and the like. Assuch, the Frenkel-Poole emission behavior of a dielectric layer isgenerally determined by the dielectric layer's bulk properties.Fowler-Nordheim emission allows the conduction of charges through adielectric layer through tunneling. As such, the Fowler-Nordheimemission behavior of a dielectric layer is generally determined by thephysical thickness of the dielectric layer. This leakage current is aprimary driving force in the adoption of high-k dielectric materials.The use of high-k materials allows the physical thickness of thedielectric layer to be as thick as possible while maintaining therequired capacitance (see Eqn 1 above).

SUMMARY OF THE DISCLOSURE

The following summary of the disclosure is included in order to providea basic understanding of some aspects and features of the disclosure.This summary is not an extensive overview of the disclosure and as suchit is not intended to particularly identify key or critical elements ofthe disclosure or to delineate the scope of the disclosure. Its solepurpose is to present some concepts of the disclosure in a simplifiedform as a prelude to the more detailed description that is presentedbelow.

In some embodiments, oxygen donor layers are formed adjacent to high-kdielectric layers to reduce the leakage current through capacitorstacks. The materials used for the oxygen donor layers are selected suchthat it is thermodynamically favorable for the oxygen donor layers toprovide oxygen to the high-k dielectric layer. Without being bound bytheory, it is believed that this donation of oxygen to the high-kdielectric material fills oxygen vacancies in the high-k dielectriclayer and reduces the leakage current.

In some embodiments, oxygen donor dopants are incorporated into high-kdielectric layer to reduce the leakage current through capacitor stacks.The materials used for the oxygen donor dopants are selected such thatit is thermodynamically favorable for the oxygen donor dopants toprovide oxygen to the high-k dielectric layer. Without being bound bytheory, it is believed that this donation of oxygen to the high-kdielectric layer fills oxygen vacancies in the high-k dielectric layerand reduces the leakage current.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The drawings are not to scale and the relative dimensionsof various elements in the drawings are depicted schematically and notnecessarily to scale.

The techniques of the present disclosure can readily be understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a flow chart describing a method for fabricating aDRAM capacitor stack in accordance with some embodiments.

FIG. 2 illustrates a simplified cross-sectional view of a DRAM capacitorstack fabricated in accordance with some embodiments.

FIG. 3 illustrates a flow chart describing a method for fabricating aDRAM capacitor stack in accordance with some embodiments.

FIG. 4 illustrates a simplified cross-sectional view of a DRAM capacitorstack fabricated in accordance with some embodiments.

FIG. 5 illustrates a simplified cross-sectional view of a DRAM memorycell fabricated in accordance with some embodiments.

FIG. 6 illustrates a simplified cross-sectional view of a DRAM memorycell fabricated in accordance with some embodiments.

DETAILED DESCRIPTION

A detailed description of one or more embodiments is provided belowalong with accompanying figures. The detailed description is provided inconnection with such embodiments, but is not limited to any particularexample. The scope is limited only by the claims and numerousalternatives, modifications, and equivalents are encompassed. Numerousspecific details are set forth in the following description in order toprovide a thorough understanding. These details are provided for thepurpose of example and the described techniques may be practicedaccording to the claims without some or all of these specific details.For the purpose of clarity, technical material that is known in thetechnical fields related to the embodiments has not been described indetail to avoid unnecessarily obscuring the description.

Metal oxide dielectric materials typically have a number of defects,including oxygen vacancies. As discussed previously, these defectscontribute to leakage current through the dielectric material via aFrenkel-Poole mechanism. Methods to reduce the concentration of oxygenvacancies in metal oxide dielectric materials include the use of annealtreatments in an oxygen-containing atmosphere after the deposition ofthe dielectric material. However, increases in the leakage current ofmetal oxide dielectric materials are sometimes observed after subsequentprocessing steps, indicating that a more permanent solution is desired.

The transport of oxygen between adjacent metal oxide materials dependsupon their relative stability, chemical potentials, and free energy offormation. The relative stability of metal oxides can be determined byusing their Ellingham diagrams. The Ellingham diagrams present thetemperature dependence of the Gibb's free energy. For metallic oxides,the Ellingham diagram is a straight line with positive slope. Metaloxides that are “lower” on the diagram (i.e. more negative Gibb's freeenergy) are more stable than metal oxides that are higher on thediagram. Therefore, metal oxides that are higher on the diagram willdonate oxygen to metal oxides that are lower on the diagram. An extremeexample is the reduction of iron oxide by aluminum to form aluminumoxide in the well known thermite reaction. The aluminum oxide has alower (i.e. more negative) Gibb's free energy change of formation thanthe iron oxide and the formation of the aluminum oxide isthermodynamically more favorable than the formation of iron oxide. Thesesame principles also hold for other metal/metal oxide or metaloxide/metal oxide pairs.

Metal oxide materials can be selected that can act as oxygen donors tothe dielectric material. The selection can include materials wherein thedielectric material may reduce (e.g. take oxygen from) the oxygen donormaterial. The oxygen donor material should have a number ofstoichiometric oxide compositions that are stable. As an example, if thedielectric material is zirconium oxide, then examples of suitable oxygendonor materials (e.g. they are above zirconium oxide on the Ellinghamdiagram) include chromium oxide, tungsten oxide, tin oxide, vanadiumoxide, titanium oxide, tantalum oxide, manganese oxide, molybdenumoxide, niobium oxide, etc. As an example, if the dielectric material istitanium oxide, then examples of suitable oxygen donor materials (e.g.they are above zirconium oxide on the Ellingham diagram) includechromium oxide, tungsten oxide, tin oxide, vanadium oxide, tantalumoxide, manganese oxide, molybdenum oxide, niobium oxide, etc.

The inclusion of the oxygen donor material in the capacitor stack shouldnot have a negative impact on the k value or the EOT of the capacitorstack. Therefore, the oxygen donor material should be moderatelyconductive so that it may be treated as part of the electrode structureand not part of the dielectric portion of the capacitor stack.

FIG. 1 describes a method, 100, for fabricating a DRAM capacitor stack.The initial step, 102, involves forming a first electrode layer on asubstrate. Examples of suitable electrode layers include metals, metalalloys, conductive metal oxides, conductive metal silicides, conductivemetal nitrides, or combinations thereof. Two particularly interestingclasses of materials are the conductive metal oxides and the conductivemetal nitrides. Optionally, the first electrode layer can then besubjected to an annealing process (not shown). If the first electrodelayer is a conductive metal nitride material, then the first electrodelayer may be annealed using a Rapid Thermal Anneal (RTA) technique orfurnace anneal technique. For the RTA case, the temperature is quicklyraised in the presence of a nitrogen containing gas such as nitrogen,forming gas, ammonia, etc. Examples of such electrode treatment stepsare further described in U.S. application Ser. No. 13/051,531 filed onMar. 18, 2011, which is incorporated herein by reference for allpurposes. Alternatively, if the first electrode is a conductive metaloxide, then the first electrode layer may be annealed in an inert orreducing atmosphere such as argon, nitrogen, or forming gas. Examples ofsuch an annealing process is further described in U.S. application Ser.No. 13/084,666 filed on Apr. 12, 2011, entitled “METHOD FOR FABRICATINGA DRAM CAPACITOR” which is incorporated herein by reference for allpurposes.

The next step, 104, involves forming a first oxygen donor layer abovethe first electrode layer. As used herein, an “oxygen donor layer” willbe understood to describe a layer wherein the material that forms thelayer has a higher (i.e., less negative) Gibb's free energy change offormation than the adjacent dielectric material. This layer may donateoxygen to the dielectric layer, thereby reducing the concentration ofoxygen vacancies, and thus reduce the leakage current of the capacitorstack as discussed previously. The thickness of the first oxygen donorlayer is typically between 1A and 25A. The next step, 106, includesforming a dielectric layer above the first oxygen donor layer. Thedielectric layer may be a single layer or may be formed from multiplelayers. The dielectric layer may include a dopant. As used herein, thedopant may be electrically active or not electrically active. Thedefinition of a “dopant” excludes residues and impurities such ascarbon, etc. that may be present in the material due to inefficienciesof the process or impurities in the precursor materials. The next step,108, includes forming a second oxygen donor layer above the dielectriclayer. The thickness of the second oxygen donor layer is typicallybetween 1A and 25A. This layer may also donate oxygen to the dielectriclayer and thus reduce the leakage current of the capacitor stack asdiscussed previously. In some embodiments, the second oxygen donor layerhas the same composition as the first oxygen donor layer. In someembodiments, the second oxygen donor layer has a different compositionfrom the first oxygen donor layer.

The crystalline phases of dielectric materials exhibit higher k valuesthan their amorphous phases. Therefore, there is often an optionalanneal step either after the dielectric formation step (also known as apost dielectric anneal (PDA)) or an anneal step after the formation ofthe second electrode (also known as a post metallization anneal (PMA))to crystallize at least a portion of the dielectric layer. Examples ofthe PDA and PMA treatments are further described in U.S. applicationSer. No. 13/159,842 filed on Jun. 14, 2011, entitled “METHOD OFPROCESSING MIM CAPACITORS TO REDUCE LEAKAGE CURRENT” which isincorporated herein by reference for all purposes.

The next step, 110, involves forming a second electrode layer above thesecond oxygen donor layer to form a capacitor stack. Typically, thecapacitor stack can then be subjected to a PMA annealing process (notshown) as discussed previously.

Those skilled in the art will appreciate that each of the firstelectrode layer, the first oxygen donor layer, the dielectric layer, thesecond oxygen donor layer, and the second electrode layer used in theDRAM MIM capacitor may be formed using any common formation techniquesuch as atomic layer deposition (ALD), plasma enhanced atomic layerdeposition (PE-ALD), atomic vapor deposition (AVD), ultraviolet assistedatomic layer deposition (UV-ALD), chemical vapor deposition (CVD),plasma enhanced chemical vapor deposition (PECVD), or physical vapordeposition (PVD). Generally, because of the complex morphology of theDRAM capacitor structure, ALD, PE-ALD, AVD, or CVD are preferred methodsof formation. However, any of these techniques are suitable for formingeach of the various layers discussed herein. Those skilled in the artwill appreciate that the teachings described herein are not limited bythe technology used for the deposition process.

In FIGS. 2, 4, 5, and 6, a capacitor stack is illustrated using a simpleplanar structure. Those skilled in the art will appreciate that thedescription and teachings herein can be readily applied to any simple orcomplex capacitor morphology. The drawings are for illustrative purposesonly and do not limit the application of the present disclosure.

FIG. 2 illustrates a simplified cross-sectional view of a DRAM capacitorstack, 200, fabricated in accordance with some embodiments. Thecapacitor stack includes a first electrode layer, a dielectric layer,and a second electrode layer. The capacitor stack may include otherlayers as well. In some embodiments, the dielectric layer includeszirconium oxide. The zirconium oxide may further include a dopant.Suitable dopants for use with zirconium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Ti, Y, orcombinations thereof. In some embodiments, the dielectric layer includestitanium oxide. The titanium oxide may further include a dopant.Suitable dopants for use with titanium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Y, Zr, orcombinations thereof. However, those skilled in the art will understandthat the present methods may be applied to many dielectric layers.Examples of suitable dielectric layers include aluminum oxide,barium-strontium-titanate (BST), hafnium oxide, hafnium silicate,niobium oxide, lead-zirconium-titanate (PZT), a bilayer of silicon oxideand silicon nitride, silicon oxy-nitride, strontium-titanate (STO),tantalum oxide, titanium oxide, zirconium oxide, or combinationsthereof. These dielectric layers may also include dopants.

First electrode layer, 202, is formed above substrate, 201. Generally,the substrate was subjected to one or more processing steps in themanufacture of a full DRAM device. First electrode layer, 202, includesone of metals, metal alloys, conductive metal oxides, conductive metalnitrides, conductive metal silicides, conductive metal carbides, etc.For this example, first electrode layer, 202, includes a conductivemetal nitride. Examples of such conductive metal nitrides include theconductive compounds of cobalt nitride, molybdenum nitride, nickelnitride, tantalum nitride, titanium nitride, titanium aluminum nitride,tungsten nitride, or combinations thereof. A specific electrode layer ofinterest is titanium nitride when zirconium oxide is used as thedielectric layer. The titanium nitride is typically formed using PVD,PECVD, CVD, or ALD as discussed previously. The titanium nitride firstelectrode layer may optionally receive an RTA anneal treatment beforethe formation of the oxygen donor layer as discussed previously.

First oxygen donor layer, 204, is then formed above the titanium nitridefirst electrode layer. The thickness of the first oxygen donor layer istypically between 1A and 25A. Suitable oxygen donor layers for use withzirconium oxide dielectric layers include one of chromium oxide, ceriumoxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, titanium oxide, tungsten oxide, vanadiumoxide, or combinations thereof. Suitable oxygen donor layers for usewith titanium oxide dielectric layers include one of chromium oxide,cerium oxide, europium oxide, manganese oxide, molybdenum oxide, niobiumoxide, tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof.

Dielectric layer, 206, is then formed above the first oxygen donorlayer. Suitable dielectric layers include at least one of aluminumoxide, barium-strontium-titanate (BST), hafnium oxide, hafnium silicate,niobium oxide, lead-zirconium-titanate (PZT), a bilayer of silicon oxideand silicon nitride, silicon oxy-nitride, strontium-titanate (STO),tantalum oxide, titanium oxide, zirconium oxide, or combinationsthereof. The dielectric layer may be a single layer or may be formedfrom multiple layers. In some embodiments, the dielectric layer includeszirconium oxide. The zirconium oxide may further include a dopant.Suitable dopants for use with zirconium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Ti, Y, orcombinations thereof. In some embodiments, the dielectric layer includestitanium oxide. The titanium oxide may further include a dopant.Suitable dopants for use with titanium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Y, Zr, orcombinations thereof.

Second oxygen donor layer, 208, is then formed above the dielectriclayer. The thickness of the second oxygen donor layer is typicallybetween 1A and 25A. Suitable oxygen donor layers for use with zirconiumoxide dielectric layers include one of chromium oxide, cerium oxide,europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, titanium oxide, tungsten oxide, vanadiumoxide, or combinations thereof. Suitable oxygen donor layers for usewith titanium oxide dielectric layers include one of chromium oxide,cerium oxide, europium oxide, manganese oxide, molybdenum oxide, niobiumoxide, tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof. In some embodiments, the second oxygen donor layerhas the same composition as the first oxygen donor layer. In someembodiments, the second oxygen donor layer has a different compositionfrom the first oxygen donor layer.

Second electrode layer, 210, is then formed above the second oxygendonor layer to form a capacitor stack. Second electrode layer, 210,includes one of metals, metal alloys, conductive metal oxides,conductive metal nitrides, conductive metal silicides, conductive metalcarbides, etc. For this example, second electrode layer, 210, includes aconductive metal nitride. Examples of such conductive metal nitridesinclude the conductive compounds of cobalt nitride, molybdenum nitride,nickel nitride, tantalum nitride, titanium nitride, titanium aluminumnitride, tungsten nitride, or combinations thereof. A specific electrodelayer of interest is titanium nitride when zirconium oxide is used asthe dielectric layer. The titanium nitride is typically formed usingPVD, PECVD, CVD, or ALD. The capacitor stack may receive a PMA treatmentas discussed previously.

FIG. 3 describes a method, 300, for fabricating a DRAM capacitor stackas described previously. The initial step, 302, involves forming a firstelectrode layer on a substrate. Examples of suitable electrode layersinclude metals, metal alloys, conductive metal oxides, conductive metalsilicides, conductive metal nitrides, or combinations thereof. Aparticularly interesting class of materials is the conductive metaloxides. Optionally, the first electrode layer can then be subjected toan annealing process (not shown). If the first electrode layer is aconductive metal nitride material, then the first electrode layer may beannealed using a Rapid Thermal Anneal (RTA) technique or furnace annealtechnique. For the RTA case, the temperature is quickly raised in thepresence of a nitrogen containing gas such as nitrogen, forming gas,ammonia, etc. as discussed previously. Alternatively, if the firstelectrode is a conductive metal oxide, then the first electrode layermay be annealed in an inert or reducing atmosphere such as argon,nitrogen, or forming gas as discussed previously.

The next step, 304, involves forming a dielectric layer above the firstelectrode layer, wherein the dielectric layer includes at least onedopant that may act as an oxygen donor dopant. As used herein, an“oxygen donor dopant” will be understood to describe a dopant wherein anoxide of the dopant has a higher (i.e. less negative) Gibb's free energychange of formation than the dielectric layer. This oxygen donor dopantmay donate oxygen to the dielectric layer, thereby reducing theconcentration of oxygen vacancies, and thus reduce the leakage currentof the capacitor stack as discussed previously. Suitable oxygen donordopants for use with zirconium oxide dielectric layer include chromiumoxide, cerium oxide, europium oxide, manganese oxide, molybdenum oxide,niobium oxide, tantalum oxide, tin oxide, titanium oxide, tungstenoxide, vanadium oxide, or combinations thereof. The oxygen donor dopantmay be added to the dielectric layer in a concentration range between 1atomic % and 20 atomic %. Suitable oxygen donor dopants for use withtitanium oxide dielectric layers include chromium oxide, cerium oxide,europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof. The oxygen donor dopant may be added to thedielectric layer in a range between 1 atomic % and 20 atomic %. Thedielectric layer may be a single layer or may be formed from multiplelayers. The dielectric layer may be subjected to a PDA treatment asdiscussed previously.

The next step, 306, involves forming a second electrode layer above thedielectric layer to form a capacitor stack. Typically, the capacitorstack can then be subjected to an annealing process (not shown) asdiscussed previously.

FIG. 4 illustrates a simplified cross-sectional view of a DRAM capacitorstack, 400, fabricated in accordance with some embodiments. In someembodiments, the dielectric layer includes zirconium oxide. In someembodiments, the dielectric layer includes titanium oxide.

First electrode layer, 402, is formed above substrate, 401. Generally,the substrate has already received several processing steps in themanufacture of a full DRAM device. First electrode layer, 402, includesone of metals, metal alloys, conductive metal oxides, conductive metalnitrides, conductive metal silicides, conductive metal carbides, etc.For this example, first electrode layer, 402, includes a conductivemetal nitride. Examples of such conductive metal nitrides include theconductive compounds of cobalt nitride, molybdenum nitride, nickelnitride, tantalum nitride, titanium nitride, titanium aluminum nitride,tungsten nitride, or combinations thereof. A specific electrode layer ofinterest is titanium nitride when zirconium oxide is used as thedielectric layer. The titanium nitride is typically formed using PVD,PECVD, CVD, or ALD. The titanium nitride first electrode layer mayoptionally receive an RTA anneal treatment before the formation of theoxygen donor layer as discussed previously.

Dielectric layer, 404, is formed above the first electrode layer,wherein the dielectric layer includes at least one oxygen donor dopant,406, that may act as an oxygen donor. This oxygen donor dopant maydonate oxygen to the dielectric layer, thereby reducing theconcentration of oxygen vacancies, and thus reduce the leakage currentof the capacitor stack as discussed previously. The dopant may beintroduced into the dielectric layer as part of the formation of thedielectric layer. Suitable oxygen donor dopants for use with zirconiumoxide dielectric layers include chromium oxide, cerium oxide, europiumoxide, manganese oxide, molybdenum oxide, niobium oxide, tantalum oxide,tin oxide, titanium oxide, tungsten oxide, vanadium oxide, orcombinations thereof. The oxygen donor dopant may be added to thedielectric layer in a range between 1 atomic % and 20 atomic %. Suitableoxygen donor dopants for use with titanium oxide dielectric layersinclude chromium oxide, cerium oxide, europium oxide, manganese oxide,molybdenum oxide, niobium oxide, tantalum oxide, tin oxide, tungstenoxide, vanadium oxide, or combinations thereof. The oxygen donor dopantmay be added to the dielectric layer in a range between 1 atomic % and20 atomic %. The dielectric layer may be a single layer or may be formedfrom multiple layers. The dielectric layer may be subjected to a PDAtreatment as discussed previously.

Second electrode layer, 408, is then formed above the dielectric layerto form a capacitor stack. Second electrode layer, 408, includes one ofmetals, metal alloys, conductive metal oxides, conductive metalnitrides, conductive metal silicides, conductive metal carbides, and thelike. For this example, second electrode layer, 408, includes aconductive metal nitride. Examples of such conductive metal nitridesinclude the conductive compounds of cobalt nitride, molybdenum nitride,nickel nitride, tantalum nitride, titanium nitride, titanium aluminumnitride, tungsten nitride, or combinations thereof. A specific electrodelayer of interest is titanium nitride when zirconium oxide is used asthe dielectric layer. The titanium nitride is typically formed usingPVD, PECVD, CVD, or ALD. The capacitor stack may receive a PMA treatmentas discussed previously.

An example of a specific application of some embodiments is in thefabrication of capacitors used in the memory cells in DRAM devices. DRAMmemory cells effectively use a capacitor to store charge for a period oftime, with the charge being electronically “read” to determine whether alogical “one” or “zero” has been stored in the associated cell.Conventionally, a cell transistor is used to access the cell. The celltransistor is turned “on” in order to store data on each associatedcapacitor and is otherwise turned “off” to isolate the capacitor andpreserve its charge. More complex DRAM cell structures exist, but thisbasic DRAM structure will be used for illustrating the application ofthis disclosure to capacitor manufacturing and to DRAM manufacturing.FIG. 5 is used to illustrate one DRAM cell, 520, manufactured using astructure as discussed previously in reference to FIG. 2. The cell, 520,is illustrated schematically to include two principle components, a cellcapacitor, 500, and a cell transistor, 502. The cell transistor isusually constituted by a MOS transistor having a gate, 518, source, 514,and drain, 516. The gate is usually connected to a word line and one ofthe source or drain is connected to a bit line. The cell capacitor, 500,has a lower or storage electrode, 504, and an upper or plate electrode,512. The storage electrode is connected to the other of the source ordrain and the plate electrode is connected to a reference potentialconductor. The cell transistor is, when selected, turned “on” by anactive level of the word line to read or write data from or into thecell capacitor via the bit line.

FIG. 5 illustrates a simplified cross-sectional view of a DRAM cellfabricated in accordance with some embodiments. In some embodiments, thedielectric layer includes zirconium oxide. The zirconium oxide mayfurther include a dopant. Suitable dopants for use with zirconium oxidedielectric layers include Al, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si,Sn, Sr, Ti, Y, or combinations thereof. In some embodiments, thedielectric layer includes titanium oxide. The titanium oxide may furtherinclude a dopant. Suitable dopants for use with titanium oxidedielectric layers include Al, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si,Sn, Sr, Y, Zr, or combinations thereof. However, those skilled in theart will understand that the present methods may be applied to manydielectric layers. Examples of suitable dielectric layers includealuminum oxide, barium-strontium-titanate (BST), hafnium oxide, hafniumsilicate, niobium oxide, lead-zirconium-titanate (PZT), a bilayer ofsilicon oxide and silicon nitride, silicon oxy-nitride,strontium-titanate (STO), tantalum oxide, titanium oxide, zirconiumoxide, or combinations thereof.

As was described previously, the cell capacitor, 500, includes a firstelectrode layer, 504, formed above substrate, 501. The first electrodelayer, 504, is connected to the source or drain of the cell transistor,502. For illustrative purposes, the first electrode has been connectedto the source, 514, in this example. First electrode layer, 504, isformed above substrate, 501. Generally, the substrate has alreadyreceived several processing steps in the manufacture of a full DRAMdevice. First electrode layer, 504, includes one of metals, metalalloys, conductive metal oxides, conductive metal nitrides, conductivemetal silicides, conductive metal carbides, etc. For this example, firstelectrode layer, 504, includes a conductive metal nitride. Examples ofsuch conductive metal nitrides include the conductive compounds ofcobalt nitride, molybdenum nitride, nickel nitride, tantalum nitride,titanium nitride, titanium aluminum nitride, tungsten nitride, orcombinations thereof. A specific electrode layer of interest is titaniumnitride when zirconium oxide is used as the dielectric layer. Thetitanium nitride is typically formed using PVD, PECVD, CVD, or ALD. TheTiN first electrode layer may optionally receive an RTA anneal treatmentbefore the formation of the dielectric layer as discussed previously.

First oxygen donor layer, 506, is then formed above the titanium nitridefirst electrode layer. Suitable oxygen donor layers for use withzirconium oxide dielectric layers include one of chromium oxide, ceriumoxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof. Suitable oxygen donor layers for use with titaniumoxide dielectric layers include one of chromium oxide, cerium oxide,europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof.

Dielectric layer, 508, is then formed above the first oxygen donorlayer. Suitable dielectric layers include at least one of aluminumoxide, barium-strontium-titanate (BST), hafnium oxide, hafnium silicate,niobium oxide, lead-zirconium-titanate (PZT), a bilayer of silicon oxideand silicon nitride, silicon oxy-nitride, strontium-titanate (STO),tantalum oxide, titanium oxide, zirconium oxide, or combinationsthereof. The dielectric layer may be a single layer or may be formedfrom multiple layers. In some embodiments, the dielectric layer includeszirconium oxide. The zirconium oxide may further include a dopant.Suitable dopants for use with zirconium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Ti, Y, orcombinations thereof. In some embodiments, the dielectric layer includestitanium oxide. The titanium oxide may further include a dopant.Suitable dopants for use with titanium oxide dielectric layers includeAl, Ce, Co, Er, Ga, Gd, Ge, Hf, La, Mg, Si, Sn, Sr, Y, Zr, orcombinations thereof.

Second oxygen donor layer, 510, is then formed above the dielectriclayer. Suitable oxygen donor layers for use with zirconium oxidedielectric layers include one of chromium oxide, cerium oxide, europiumoxide, manganese oxide, molybdenum oxide, niobium oxide, tantalum oxide,tin oxide, tungsten oxide, vanadium oxide, or combinations thereof.Suitable oxygen donor layers for use with titanium oxide dielectriclayers include one of chromium oxide, cerium oxide, europium oxide,manganese oxide, molybdenum oxide, niobium oxide, tantalum oxide, tinoxide, tungsten oxide, vanadium oxide, or combinations thereof. In someembodiments, the second oxygen donor layer has the same composition asthe first oxygen donor layer. In some embodiments, the second oxygendonor layer has a different composition from the first oxygen donorlayer.

Second electrode layer, 512, is then formed above the second oxygendonor layer to form a capacitor stack. Second electrode layer, 512,includes one of metals, metal alloys, conductive metal oxides,conductive metal nitrides, conductive metal silicides, conductive metalcarbides, etc. For this example, second electrode layer, 512, includes aconductive metal nitride. Examples of such conductive metal nitridesinclude the conductive compounds of cobalt nitride, molybdenum nitride,nickel nitride, tantalum nitride, titanium nitride, titanium aluminumnitride, tungsten nitride, or combinations thereof. A specific electrodelayer of interest is titanium nitride when zirconium oxide is used asthe dielectric layer. The titanium nitride is typically formed usingPVD, PECVD, CVD, or ALD. The capacitor stack may receive a PMA treatmentas discussed previously.

Another example of a specific application of some embodiments is in thefabrication of capacitors used in the memory cells in DRAM devices. FIG.6 is used to illustrate one DRAM cell, 620, manufactured using astructure as discussed previously in reference to FIG. 4. The cell, 620,is illustrated schematically to include two principle components, a cellcapacitor, 600, and a cell transistor, 602. The cell transistor, 602, isusually constituted by a MOS transistor having a gate, 618, source, 614,and drain, 616. The gate, 618, is usually connected to a word line (notshown) and one of the source or drain is connected to a bit line (alsonot shown). The cell capacitor, 600, has a lower or storage electrode,604, and an upper or plate electrode, 612. The storage electrode isconnected to the other of the source or drain and the plate electrode isconnected to a reference potential conductor. The cell transistor is,when selected, turned “on” by an active level of the word line to reador write data from or into the cell capacitor via the bit line.

The example illustrated in FIG. 6 will use zirconium oxide as thedielectric layer. However, those skilled in the art will understand thatthe present methods may be applied to many dielectric layers. Examplesof suitable dielectric layers include aluminum oxide,barium-strontium-titanate (BST), hafnium oxide, hafnium silicate,niobium oxide, lead-zirconium-titanate (PZT), a bilayer of silicon oxideand silicon nitride, silicon oxy-nitride, strontium-titanate (STO),tantalum oxide, titanium oxide, zirconium oxide, or combinationsthereof. The dielectric layer includes at least one oxygen donor dopantthat may act as an oxygen donor. This oxygen donor dopant may donateoxygen to the dielectric layer, thereby reducing the concentration ofoxygen vacancies, and thus reduce the leakage current of the capacitorstack as discussed previously. The dopant may be introduced into thedielectric layer as part of the formation of the dielectric layer.Suitable oxygen donor dopants for use with zirconium oxide dielectriclayers include chromium oxide, cerium oxide, europium oxide, manganeseoxide, molybdenum oxide, niobium oxide, tantalum oxide, tin oxide,titanium oxide, tungsten oxide, vanadium oxide, or combinations thereof.The oxygen donor dopant may be added to the dielectric layer in a rangebetween 1 atomic % and 20 atomic %. Suitable oxygen donor dopants foruse with titanium oxide dielectric layers include chromium oxide, ceriumoxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof. The oxygen donor dopant may be added to thedielectric layer in a range between 1 atomic % and 20 atomic %.

As was described previously, the cell capacitor, 600, includes a firstelectrode layer, 604, formed above substrate, 601. The first electrodelayer, 604, is connected to the source or drain of the cell transistor,602. For illustrative purposes, the first electrode has been connectedto the source, 614, in this example. Generally, the substrate hasalready received several processing steps in the manufacture of a fullDRAM device. First electrode layer, 604, includes one of metals, metalalloys, conductive metal oxides, conductive metal nitrides, conductivemetal silicides, conductive metal carbides, etc. For this example, firstelectrode layer, 604, includes a conductive metal nitride. Examples ofsuch conductive metal nitrides include the conductive compounds ofcobalt nitride, molybdenum nitride, nickel nitride, tantalum nitride,titanium nitride, titanium aluminum nitride, tungsten nitride, orcombinations thereof. A specific electrode layer of interest is titaniumnitride when zirconium oxide is used as the dielectric layer. Thetitanium nitride is typically formed using PVD, PECVD, CVD, or ALD. Thetitanium nitride first electrode layer may optionally receive an RTAanneal treatment before the formation of the dielectric layer asdiscussed previously.

Dielectric layer, 608, is formed above the first electrode layer,wherein the dielectric layer includes at least one dopant that may actas an oxygen donor dopant, 606. This oxygen donor dopant may donateoxygen to the dielectric layer, thereby reducing the concentration ofoxygen vacancies, and thus reduce the leakage current of the capacitorstack as discussed previously. The dopant may be introduced into thedielectric layer as part of the formation of the dielectric layer.Suitable oxygen donor dopants for use with zirconium oxide dielectriclayers include chromium oxide, cerium oxide, europium oxide, manganeseoxide, molybdenum oxide, niobium oxide, tantalum oxide, tin oxide,titanium oxide, tungsten oxide, vanadium oxide, or combinations thereof.The oxygen donor dopant may be added to the dielectric layer in a rangebetween 1 atomic % and 20 atomic %. Suitable oxygen donor dopants foruse with titanium oxide dielectric layers include chromium oxide, ceriumoxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide,tantalum oxide, tin oxide, tungsten oxide, vanadium oxide, orcombinations thereof. The oxygen donor dopant may be added to thedielectric layer in a range between 1 atomic % and 20 atomic %. Thedielectric layer may be a single layer or may be formed from multiplelayers. The dielectric layer may be subjected to a PDA treatment asdiscussed previously.

Second electrode layer, 612, is then formed above the dielectric layerto form a capacitor stack. Second electrode layer, 612, includes one ofmetals, metal alloys, conductive metal oxides, conductive metalnitrides, conductive metal silicides, conductive metal carbides, etc.For this example, second electrode layer, 612, includes a conductivemetal nitride. Examples of such conductive metal nitrides include theconductive compounds of cobalt nitride, molybdenum nitride, nickelnitride, tantalum nitride, titanium nitride, titanium aluminum nitride,tungsten nitride, or combinations thereof. A specific electrode layer ofinterest is titanium nitride when zirconium oxide is used as thedielectric layer. The titanium nitride is typically formed using PVD,PECVD, CVD, or ALD. The capacitor stack may receive a PMA treatment asdiscussed previously.

Although the foregoing examples have been described in some detail forpurposes of clarity of understanding, the disclosure is not limited tothe details provided. There are many alternative ways of implementingthe teachings. The disclosed examples are illustrative and notrestrictive.

1. A method for forming a capacitor stack, the method comprising: forming a first layer on a substrate, wherein the first layer is operable as a first electrode layer of the capacitor stack; forming a second layer above the first layer, wherein the second layer is operable as a dielectric layer, wherein the second layer further comprises a dielectric material and an oxygen donor dopant, wherein the dielectric material comprises one of zirconium oxide or titanium oxide, and wherein the oxygen donor dopant comprises one of chromium oxide, europium oxide, manganese oxide, molybdenum oxide, tin oxide, tungsten oxide, vanadium oxide, or combinations thereof; and forming a third layer above the second layer, wherein the third layer is operable as a second electrode layer of the capacitor stack.
 2. (canceled)
 3. The method of claim 1, wherein the first layer and the third layer each comprises one of a metal, a metal alloy, a conductive metal oxide, a conductive metal nitride, a conductive metal silicide, or a conductive metal carbide.
 4. The method of claim 3, wherein the first layer and the third layer each comprises a conductive metal nitride.
 5. The method of claim 4, wherein the first layer and the third layer each comprises titanium nitride.
 6. The method of claim 1, wherein the dielectric material of the second layer comprises zirconium oxide.
 7. The method of claim 6, wherein a concentration of the oxygen donor dopant in the second layer is between 1 atomic % and 20 atomic %.
 8. The method of claim 7, further comprising annealing the substrate comprising the first layer and the second layer before forming the third layer.
 9. The method of claim 8, further comprising annealing the capacitor stack after the forming of the third layer.
 10. The method of claim 1, wherein the dielectric material of the second layer comprises titanium oxide.
 11. The method of claim 10, wherein a concentration of the oxygen donor dopant in is added to the second layer is in a range between 1 atomic % and 20 atomic %.
 12. The method of claim 11, further comprising annealing the substrate comprising the first layer and the second layer before forming the third layer.
 13. The method of claim 12, further comprising annealing the capacitor stack after the forming of the third layer.
 14. The method of claim 1, wherein the oxygen donor dopant is operable to donate oxygen to the dielectric material and to reduce a concentration of oxygen vacancies within the dielectric material.
 15. The method of claim 1, wherein the oxygen donor dopant is introduced into the dielectric layer as a part of the dielectric layer.
 16. A method for forming a capacitor stack, the method comprising: forming a first layer on a substrate, wherein the first layer comprises one of a metal, a metal alloy, a conductive metal oxide, a conductive metal nitride, a conductive metal silicide, or a conductive metal carbide; forming a second layer above the first layer, wherein the second layer is operable as a first oxygen donor layer, wherein the second layer comprises one of chromium oxide, cerium oxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide, tin oxide, tungsten oxide, vanadium oxide, or combinations thereof; forming a third layer above the second layer; forming a fourth layer above the third layer, wherein the fourth layer is operable as a second oxygen donor layer, wherein the fourth layer comprises one of chromium oxide, cerium oxide, europium oxide, manganese oxide, molybdenum oxide, niobium oxide, tin oxide, tungsten oxide, vanadium oxide, or combinations thereof; and forming a fifth layer above the fourth layer, wherein the fifth layer comprises one of a metal, a metal alloy, a conductive metal oxide, a conductive metal nitride, a conductive metal silicide, or a conductive metal carbide, and wherein the second layer and the fourth layer each have a Gibb's free energy that is higher than a material included in the third layer.
 17. The method of claim 16, wherein the second layer and the fourth layer comprise the same material.
 18. The method of claim 16, wherein the second layer and the fourth layer comprise different materials.
 19. The method of claim 16, wherein the third layer comprises one of aluminum oxide, barium-strontium-titanate (BST), hafnium oxide, hafnium silicate, niobium oxide, lead-zirconium-titanate (PZT), a bilayer of silicon oxide and silicon nitride, silicon oxy-nitride, strontium-titanate (STO), tantalum oxide, titanium oxide, or zirconium oxide.
 20. The method of claim 16, wherein the third layer comprises zirconium oxide.
 21. The method of claim 16, wherein the third layer comprises titanium oxide. 